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To work around this problem, instead of having a single time. Just pass in the number you want to round, plus an optional second argument representing how many digits after the decimal point you want to round it to. If you omit the second argument, round rounds your number to the nearest whole integer. It says it can do this in the license agreement you agreed to. You can write a simple stopwatch program yourself in Python. This means your code will need to do the following:. Find the current time by calling time. Open a new file editor window and save it as stopwatch.

Your program should also print some brief instructions to the user before calling input , so the timer can begin after the user presses ENTER.

Writing your own programming language and compiler with Python

Then the code will start tracking lap times. Enter the following code into the file editor, writing a TODO comment as a placeholder for the rest of the code:. Press Ctrl-C to quit. Add the following code to your program:. When a lap ends, we calculate how long the lap took by subtracting the start time of the lap, lastTime , from the current time, time. Since the results of these time calculations will have many digits after the decimal point such as 4. After printing the lap information, we get ready for the next lap by adding 1 to the count lapNum and setting lastTime to the current time, which is the start time of the next lap.

Time tracking opens up several possibilities for your programs. Although you can download apps to do some of these things, the benefit of writing programs yourself is that they will be free and not bloated with ads and useless features. You could write similar programs to do the following:. Add a feature to your program to display the elapsed time since a process started, such as a download that uses the requests module.

Intermittently check how long a program has been running and offer the user a chance to cancel tasks that are taking too long. The time module is useful for getting a Unix epoch timestamp to work with. But if you want to display a date in a more convenient format, or do arithmetic with dates for example, figuring out what date was days ago or what date is days from now , you should use the datetime module.

The datetime module has its own datetime data type. This object includes the year, month, day, hour, minute, second, and microsecond of the current moment. You can also retrieve a datetime object for a specific moment by using the datetime.

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A Unix epoch timestamp can be converted to a datetime object with the datetime. The date and time of the datetime object will be converted for the local time zone. Passing time. So the expressions datetime.

These examples were entered on a computer set to Pacific Standard Time. The datetime module also provides a timedelta data type, which represents a duration of time rather than a moment in time. The datetime. A timedelta object has the total duration represented in days, seconds, and microseconds. These numbers are stored in the days , seconds , and microseconds attributes, respectively. Passing a timedelta object to str will return a nicely formatted, human-readable string representation of the object.

In this example, we pass keyword arguments to datetime. Finally, passing the timedelta object to str returns a string clearly explaning the duration. The arithmetic operators can be used to perform date arithmetic on datetime values. For example, to calculate the date 1, days from now, enter the following into the interactive shell:. Then make a timedelta object for a duration of 1, days and store it in thousandDays. Add dt and thousandDays together to get a datetime object for the date 1, days from now. Python will do the date arithmetic to figure out that 1, days after February 27, , will be November 23, This is useful because when you calculate 1, days from a given date, you have to remember how many days are in each month and factor in leap years and other tricky details.

The datetime module handles all of this for you.

Embracing the Four Python Programming Styles

Subtracting aboutThirtyYears from oct21st gives us a datetime object for the date 30 years before October 21, By using a while loop, you can pause your programs until a specific date. For example, the following code will continue to loop until Halloween Rather, the while loop will just check the condition once per second and continue with the rest of the program after Halloween or whenever you program it to stop. Use the strftime method to display a datetime object as a string. The f in the name of the strftime function stands for format.

Julia in a Nutshell

Year without century, '00' to '99' to Month as a decimal number, '01' to '12'. Day of the month, '01' to '31'. Day of the year, '' to ''. Day of the week, '0' Sunday to '6' Saturday. Hour hour clock , '00' to '23'. Hour hour clock , '01' to '12'. Minute, '00' to '59'. Second, '00' to '59'. The strptime function is the inverse of the strftime method. A custom format string using the same directives as strftime must be passed so that strptime knows how to parse and understand the string.

The p in the name of the strptime function stands for parse. The string with the date information must match the custom format string exactly, or Python will raise a ValueError exception. Dates and times in Python can involve quite a few different data types and functions.

Writing the “Hello, World!” Program

A Unix epoch timestamp used by the time module is a float or integer value of the number of seconds since 12 AM on January 1, , UTC. A datetime object of the datetime module has integers stored in the attributes year , month , day , hour , minute , and second. A timedelta object of the datetime module represents a time duration, rather than a specific moment.

If hour , minute , or second arguments are not provided, they default to 0.

How To Use Functions In Python (Python Tutorial #3)

Say you want to schedule some code to run after a delay or at a specific time. You could add code like the following at the start of your program:. Your program cannot do anything while waiting for the loop of time. This is because Python programs by default have a single thread of execution.

A single-threaded program has only one finger. But a multithreaded program has multiple fingers. Each finger still moves to the next line of code as defined by the flow control statements, but the fingers can be at different places in the program, executing different lines of code at the same time. All of the programs in this book so far have been single threaded.

Rather than having all of your code wait until the time. The separate thread will pause for the time. Meanwhile, your program can do other work in the original thread.